Optical interaction device

ABSTRACT

A laser beam is subjected to repeated reflection by a plurality of concave mirrors disposed in a confronting arrangement. Reflecting paths are centralized to form an interactive region of a high photon density. An interaction target such as gas, liquid, a solid body, plasma, a particle beam and an electron beam is introduced into the interactive region. Interaction with the laser beam causes optical interactions such as optical excitement, optical ionization, optical dissociation, optical synthesis, optical generation and optical analysis.

TECHNICAL FIELD

The present invention relates to a device on which a laser beam isreflected multiple times by a plurality of confronting concave mirrors,the reflected optical path is centralized to form an interactive regionof high photon density, and an interaction target such as gas, liquid, asolid body, plasma, a particle beam or an electron beam is introducedinto the interactive region to cause an optical interaction such asoptical excitation, optical ionization, photolysis, opticaldissociation, photosynthesis, optical generation and optical analysis.

TECHNICAL BACKGROUND

Gas, liquid, solid bodies and particle beams perform strong opticalinteractions with laser beams of specified wavelengths corresponding tothe atoms and molecules composing them. In order to cause suchinteractions in the conventional arts, a pair of confronting curvilinearmirrors are generally used for forming an optical resonator in whichoptical interactions are carried out.

In this case, a region of high photon density is centralized to thecenter of the resonator interior. Such a region is extremely too smalland too short to reserve long interaction time of atoms and moleculespassing through the region. In order to reserve sufficient possibilityto store light, an aperture formed through each curvilinear mirror isdesigned as small as possible to reduce optical loss. As a result,introduction of beams, atoms and molecules into the interactive regionis rendered to be highly difficult to practice sufficiently. It isadditionally a recent trend to use laser beams of extremely shortpulses. Use of such laser beams makes the interactive region extremelysmall in terms of time and space dimension and, consequently, it isalmost infeasible to cause optical interactions effectively.

Use of gas flows and particle beams for optical interaction necessitatespresence of large apertures for incidence and exit into and out of theinteractive region. In addition, these interaction media are in mostcases rather low in density and degree of interaction. In order to causesufficient optical interactions of the gas flows and particle beams withthe laser beam, it is necessary to reserve a large interaction region interms of time and space dimension.

SUMMARY OF THE INVENTION

It is thus the primary object of the present invention to provide anovel optical interaction device which removes the above-describedproblems inherent to the conventional arts and assures high efficiencyin use of laser beams.

It is another object of the present invention to provide an opticalinteraction device which is able to reserve large apertures forincidence and exit of interaction media and interaction targets, a largeinteractive region with high photon density and along interaction time.

According to the present invention, an optical interaction deviceincludes a pair of confronting first and second mirror sets each ofwhich is made up of a plurality concave mirrors disposed in a annulararrangement around a common axis of the interactive region.

A laser beam generated by laser beam generating means is led to oneconcave mirror selected from the first mirror set via a laser beam guidemeans. Each concave mirror in the first mirror set reflects an incidentbeam to pass it through a prescribed position on an axis of theinteractive region to direct a reflected beam to a corresponding concavemirror in the second mirror set. As a result, an interactive region ofhigh photon density is formed at a position where reflected beams arecentralized.

Each concave mirror in the second mirror set reflects incident beam froma corresponding concave mirror in the first mirror set to direct it toan adjacent concave mirror. As a consequence, each laser beamreciprocates between the first and second mirror sets whilstsequentially moving in the circumferential direction of the first andsecond mirror sets.

Interaction between the laser beams and the interaction target takesplaces in an interaction region where the laser beams pass collectively.

On the optical interaction device in accordance with the presentinvention, incident laser beams to the concave mirrors of the first,mirror set are reflected in a collected fashion and centralized at afocus on an axis of the interactive region. Then, each reflected beamcan be directed to a corresponding concave mirror of the second mirrorset. Thus, a interaction region of high photon density can be formed ata position where the reflected beams are centralized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the diagrammatic view of the optical interaction device inaccordance with the present invention, in which (a) is a side plan view,and, (b) and (c) are front plan view of respective mirror sets,

FIG. 2 indicates laser beam optical paths of laser beams reciprocatingthe mirrors sets, in which (a) shows the going optical path and (b)shows the return optical path,

FIG. 3 shows the optical interaction of as with laser beams on theoptical interaction device in accordance with the present invention,

FIG. 4 shows a process for producing a laser beam with wavelengthconversion by the optical interaction device in accordance with thepresent invention,

FIG. 5 shows a charge converter incorporating the optical interactiondevice in accordance with the present invention,

FIG. 6 shows a multi charged ion source incorporating the opticalinteraction device in accordance with the present invention,

FIG. 7 shows a micro analyzer incorporating the optical interactiondevice in accordance with the present invention,

FIG. 8 shows a micro analyzer incorporating the optical interactiondevice in accordance with the present invention,

FIG. 9 shows a micro dissociation device incorporating the opticalinteraction device in accordance with the present invention, and

FIG. 10 shows dual phase excitation process performed on the opticalinteraction device in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the present invention shall be hereinafterdescribed in reference to the accompanying drawings, in which FIG. 1shows a diagrammatic view of the optical interaction device inaccordance with the present invention. In FIG. 1, (a) is a side planview and (b) as well as (c) are front plan view of the respective mirrorsets. The optical paths of laser beams reciprocating between the mirrorsets A and B are shown in FIG. 2.

The optical interaction device 11 includes a pair of mirror sets A and Bdisposed in a confronting arrangement. The mirror set A includesmultiple concave mirrors A1, A2 to An which are disposed annularlyaround an axis of the interactive region O of beams. Similarly, themirror set B includes multiple concave mirrors B1, B2 to Bn which aredisposed annularly around an axis of the interactive region O of beams.

In the case of the illustrated embodiment, each mirror set A or Bincludes twelve concave mirrors (n=12). An aperture Ap is formed on theinner side of each annular arrangement of the concave mirrors forintroduction of electron beams. Although the mirrors of the mirror setsA and B appear to be disposed on curved planes in the illustration inorder to show that the concave mirrors have a same focal length, theconcave mirrors are disposed on flat planes in practice.

Each concave mirror An of the mirror set A reflects an incident laserbeam to focus the same at a prescribed position on the axis of theinteractive region O and the reflected laser beam is directed to acorresponding concave mirror Bn of the mirror set B. Here, the opticalpath L1 of the laser beam traveling from the concave mirror An to theconcave mirror Bn whilst passing the focus is hereinafter referred to as“a forward trajectory”.

Each concave mirror Bn of the mirror set B reflects an incident laserbeam from a corresponding concave mirror An of the mirror set A todirect the same to an adjacent concave mirror An+1, the adjacent concavemirror being biased from the concave mirror in the direction of Φ. Here,the optical path L2 of the laser beam traveling from the concave mirrorBn to the concave mirror Bn+1 is hereinafter referred to as “a returntrajectory”.

Therefore, the laser beams introduced to the mirror sets A and Bsequentially shift their reflected beams in the circumferentialdirection Φ of the annular arrangement of the concave mirrors. Statedotherwise, the beams travel from A1 to B1, from B1 to A2, from A2 toB2 - - - from An to Bn and from Bn to An+1, respectively. In FIG. 1,only the optical paths of reciprocating laser beams from A1 to A6 areshown for simplification purposes.

The inter-mirror distance of the forward trajectory L1 from a concavemirror An to a corresponding concave mirror is set to 2Z and the radiusof curvature of the concave mirror are set to 2Z. When a laser beam isincident in a parallel mode to the concave mirror A1 from the positionof the concave mirror B1 via, for example, a telescope in thearrangement shown in FIG. 1, the laser beam reflected from the concavemirror A1 focuses at a point Oa on the axis of the interactive regionand, thereafter reaches at the concave mirror B1 in a diverged mode.Since the concave mirrors A1 and B1 have a same focal length, the laserbeam L2 reflected by the concave mirror B1 travels to the concave mirrorA2 in a parallel mode. The laser beam reflected by the concave mirror A2focuses at the point Oa. This process is sequentially repeated. In thisprocess, the laser beams L1 in the forward trajectory all focus at thepoint Oa and the laser beams L2 in the return trajectory all travel in aparallel mode.

When a laser beam is incident to the concave mirror A1 in a convergedmode, the reflected laser beam travels in a parallel mode. So, all laserbeams L1 reflected by the concave mirrors A travel, after passing thepoint Oa on the axis of the interactive region, in a parallel modetowards the concave mirrors B. Upon reflection by the concave mirrors B,the laser beams travel in a converged mode towards the concave mirrorsA. Sequential reflections are repeated all in this mode. During thisprocess, the laser beams in a parallel mode are all centralized at thepoint Oa to form an interaction region of a high photon density aroundthe point Oa. The reflected laser beams L2 in the return trajectory arealso collected within an narrow region around the point Oa. So, thelaser beams L2 in the return trajectory may also be utilized for theoptical interaction.

When a laser beam is incident from the position of B12 whereat noconcave mirror is provided, the laser beam exits from the position ofB12 after travel between the mirror sets A and B. Consequently, it ispossible to introduce a laser beam into the system by an outside opticalcircuit including an optical switch to rotate the polarization planeover 90 degrees, reflect it several times for repeated incidences,thereby storing laser beams in the region between the mirror sets A andB. Laser beams can be introduced into the system constantly whenwavelength is change by a secondary harmonics generator. The manner andincident and exit positions of laser beams are not limited to theabove-described designs.

When a beam is incident to a concave mirror with inclination to itsoptical axis, the resultant image is distorted due to aberration.Distortion can, however, be offset at every 180 degree of rotation byreflecting the beam whilst rotating the concave mirror in the directionof Φ. As a result, reflection can be repeated over a long distance. Thenumber of reciprocation of a laser beam between the mirror sets A and Bdependent upon the reflection loss of the mirrors involved in theprocess. Even taking into consideration the fact that the photon densitylowers to 0.999 times after the first reflection and to 0.999² timesafter the second reflection, a 1000 times of photon density can beobtained as a whole at the point where the beams cross. This is because1 divided by (1-0.999) is equal to 1000.

Therefore, when an interaction target such as gas, liquid, a solid body,plasma, particle beams and electron beams are introduce along the axisinto the region between the mirror sets A and B, laser beams and theinteraction target perform a desired interaction within the interactiveregion near the point Oa whereat the laser beams focus.

Laser beam pulses shored at the above-described optical interactiondevice are classified into the following three types.

(1) Storage of a single short pulse. Only one high output pulse shorterthan the inter-mirror distance is introduced into the system so that apulse train should repeatedly interact with electron beams. The periodof pulse is as long as the time for travel between mirrors.

(2) Storage of multiple short pulses. A plurality of pulses, each ofwhich has a period of pulse as long as the time for travel betweenmirrors, are introduced into the system for storage within a regionbetween mirror sets.

(3) Storage of a long pulse. A pulse longer than the inter-mirrordistance is used so that a laser beam should always be present betweenmirror sets.

When laser beams are introduced into the system in either of the threemodes, the laser beams are collected at the center of the region betweenthe mirror sets, whereat optical paths cross, to enhance photon density.

When particle beams of a velocity V are introduced into the interactiveregion F, the optical energy density is increased to γ (1−β·cos θ) timesdue to Einsteinian Lorentz transformation whereas the wavelength isreduced to 1/γ(1−β·cos θ) times due to Doppler effect. Here, β is equalto V/C, γ is epual to (1−β²)^(−½), and θ is the cross angle between aflux of laser beams and particle beams. Through tactful choice of theparticle beam velocity and the cross angel, effective laser output canbe enhanced and expedient selection and adjustment of laser beamwavelength can be achieved.

[For Optical Interaction of Gaseous Atoms or Molecules ]

As shown in FIG. 3, gas G is passed, as an interaction target, throughthe interactive region F in the optical interaction device in accordancewith the present invention to cause optical interactions such as opticalexcitation with laser beams L.

For example, laser beams of a proper wavelength are selected and aninteractive region F is formed in a duct and gas G such as dioxin gas orNoX gas is introduced into the interactive region F to cause efficientoptical dissociation of the interaction target. When oxygen gas G isintroduced, ozone can be synthesized optically. Namely, through opticalinteraction of gaseous atoms or molecules with laser beams within theinteractive region, optical photolysis, optical synthesis, opticalanalysis and other optical treatments can be performed.

[For Generation of Laser Beams with Wavelength Conversion by Interactionwith Liquid or a Solid Body ]

As shown in FIG. 4, a liquid or solid conversion element CE is placed asan interaction target in an interactive region F. Optical excitation iscaused by use of proper laser beams and laser beams of a specifiedwavelength are oscillated by an optical resonator RE arranged on theaxis O of the interactive region. The liquid or solid conversion elementCE is introduced through an inlet IN and placed in the interactiveregion F for excitation by laser beams L, thereby generating laser beamswith wavelength conversion. An wavelength converted laser beam L3 isstored at an optical resonator RE for intended use.

[For Charge Conversion of Particle Beams]

As shown in FIG. 5, laser beams L generated by a laser beam generator LAare introduced into a space between mirror sets A and B to form aninteractive region F. When a high energy hydrogen beam H⁰ is introducedas an interaction target into the interactive region F, the beam isexcited efficiently through optical interaction with the laser beams L.

An excited hydrogen beam is ionized within a magnetic field generated bycharge converting magnets U which are arranged embracing the interactiveregion F for charge conversion. Ionized hydrogen ion H⁺ is subjected forreciprocation between the mirror sets A and B via a ring accelerator RA.In this case, the interactive region F is utilized for charge conversionof the ring accelerator RA.

[For use as a multivalent ion source]

As shown in FIG. 6, an ion beam IB from an ion source is introduced intoan interactive region F. Lots of electrons are stripped off the ion beamthrough optical ionization to form multivalent ion with high charge.More specifically, laser beams L generated at a laser generator LA areintroduced into a space between mirror sets A and B to form aninteractive region F. An ion beam IB from the ion source is introducedinto the interactive region F in which the ion beam is excited toincrease charge and generate a multivalent ion beam.

The multivalent ion beam is accelerated at an accelerator. In anexample, a monovalent oxygen ion beam from the ion source is introducedinto the interactive region F to generate a octavalent ion beam which isaccelerated at the accelerator to an energy of eight times higher.

[For Use as a Micro Analyzer]

When the optical interaction device in accordance with the presentinvention is used for micro analyzer, a vacuum change V is provided inconnection with a duct D for flow of exhaust gas G as shown in FIG. 7.The vacuum chamber V is associated with a vacuum pump 21 for evacuationthereof. The duct D is provided with a compressor 6 for provisionalcompression of the exhaust gas G. The exhaust gas G is passed to anozzle N via a shutter valve of the compressor 6 for ejection into thevacuum chamber V. This ejection causes inflation and cooling of theexhaust gas G. The nozzle N is disposed with its mouth being directed tothe interactive region F.

The optical interaction device 11 performs resonance ionization ofmicro-components such as dioxin within the exhaust gas G. Laser beams Lare supplied into the optical interaction device 11 from a given sourceoutside the vacuum chamber V. A laser beam generator LA, an opticalswitch 7, a polariscope 8 and reflection mirrors 9 are disposed outsidethe vacuum chamber V for selection of laser beams of a specifiedwavelength in accordance with the kind of the micro-component such asdioxin and for supply into the optical interaction device 11.

Laser beams of a specified wavelength is capable of ionizing a specifiedsubstance through resonance. For example, a long pulse system is appliedto ionization of dioxin. When high output laser beams of about twonano-meter wavelength are used, only electrons can be stripped off thedioxin for ionization without causing any decomposition of dioxinmolecules.

The vacuum chamber V is provided with a collection guide 10 for electricabsorption of ions. The collection guide 10 captures ionized dioxin byits electric charge. The dioxin so captured by the collection guide 10is passed to an analyzer 12 of travel time and mass. The resultant massspectrum is visually indicated on a monitor 13. Quantitative andqualitative analysis of dioxin can be carried out on the basis of theresultant mass spectrum.

[For Removal of Harmful Micro-component]

As shown in FIG. 8, the optical interaction device in accordance withthe present invention is disposed in a duct for exhaust gas G and athrottle 15 is disposed therein in order to ionize dioxin by a shortpulse process. In this case, no compression of the exhaust gas isemployed since only decomposition and harmlessness of the dioxin areintended without any need for high degree sensitivity. Therefore,interaction is carried out under atmospheric conditions.

[For Use as an X-ray Beam Generator]

In the arrangement shown in FIG. 9, the optical interaction device inaccordance with the present invention is used for generation of an X-raybeam. In the illustration, 11 indicates the optical interaction device,LA indicates a laser beam generator, 23 indicates a SHG (secondaryharmonics generator), 24 indicates a dichroic mirror and A and Bindicate mirror sets which are disposed within a vacuum chamber V.

A laser beam L of a selected wavelength is introduced into the opticalinteraction device 11 and an interactive region F of a high photondensity is formed by centralization of the laser beam L. An electronbeam e is introduced into the interactive region f in the vacuum chamberV along the axis O of the interactive region for interaction with thelaser beam 1.

It is understood that the laser beam made up of optical particlescrashes against the electron beam to generate an X-ray beam throughdispersion of photon beam. When a laser beam, i.e. a sufficientlypowerful electromagnetic wave, is used as an undulator whichperiodically applies electromagnetic power, X ray emission is resulted.In the illustration, X indicates an X ray generated by inverse Comptonscattering or interaction with the undulator and Ef indicates scatteredelectron.

[For Two Step Excitation]

As shown in FIG. 10, the interaction device 11 includes two pairs ofmirror sets A, B·A′ and B′ which arranged side by side so as to have acommon interactive region F. Laser beams L and L′ of differentwavelength are introduced into the system. For example, IR laser beamand YAG-2nd laser beam are used. When A particle beam PB is introducedas an interactive target, the first step optical interaction isperformed by the YAG-2nd laser beam and the second step opticalinteraction is performed by the IR laser beam.

POSSIBILITY OF INDUSTRIAL APPLICATION

The present invention can be employed in industrial fields in whichoptical interactions such as optical excitation, optical ionization,optical photolysis, optical dissociation, photosynthesis, opticalgeneration and optical analysis are performed through interaction oflaser beams of a specified wavelength with gaseous atoms and molecules,liquids and solid bodies.

What is claimed is:
 1. An optical interaction device comprising: firstand second mirror sets which are arranged in a confronting orientationso as to form an optical interactive region with centralized laserbeams, each set including a plurality of concave mirrors oriented inannular arrangement around a common axis, means for generating laserbeams for repeated reflection between said mirror sets, laser beam guidemeans for introducing said laser beams into said interactive region andfor outputting therefrom after prescribed number of reciprocalreflections between said first and second mirror sets, and means forintroducing an interaction target into said interactive region each saidconcave mirror in said first mirror set is oriented in an arrangementsuch that an incident laser beam is reflected towards a correspondingconcave mirror in said second mirror set, each said concave mirror insaid second mirror set is oriented in an arrangement such that anincident beam from a corresponding concave mirror in said first mirrorset is reflected towards a concave mirror adjacent to said correspondingconcave mirror, thereby sequentially shifting reflected beams in acircumferential direction of said mirror sets, a laser beam reflected byone of each concave mirror of said first mirror set and said secondmirror set is in a converged mode whereas a laser beam reflected by theother of each concave mirror of said first mirror set and said secondmirror set is in a parallel mode, said concave mirrors are oriented sothat either of said converged mode laser beam and parallel mode laserbeam pass a prescribed position on said common axis, and an opticalinteractive region is formed through centralization of laser beamsreflected towards said prescribed position on said common axis.
 2. Theoptical interaction device as claimed in claim 1, wherein a distancebetween said confronting concave mirrors is set to be equal to theradius of curvature of said each said concave mirror.
 3. The opticalinteraction device as claimed in claim 1, wherein at least two of saidfirst and second mirror sets, said laser beam generating means and saidlaser beam guide means are arranged to have said optical interactiveregion at a common position, and laser beams of different wavelengthsare introduced into means for storing laser beams, thereby centralizinga plurality of lasers of different wavelengths at said opticalinteractive region.
 4. The optical interaction device as claimed inclaim 1, wherein at least two laser beam storing means including saidfirst mirror set, said second mirror set, said laser beam generatingmeans and said laser beam guide means have said interactive region at acommon position, and laser beams of different wavelengths are introducedinto said laser beam storing means, thereby collecting a plurality oflaser beams of different wavelengths at said interactive region.
 5. Theoptical interaction device as claimed in claim 1, wherein saidinteraction target introduced into said interactive region includeparticle beams which increase substantial output of said laser beam orperform selection of laser beam wavelengths through interaction withsaid laser output of said laser beam or performs selection of thewavelength of said laser beams.
 6. The optical interaction device asclaimed in claim 1, wherein said interaction target introduced into saidinteractive region includes a wavelength converting element whichperform wavelength conversion through interaction with said laser beams.7. The optical interaction device as claimed in claim 1, wherein saidinteraction target introduced into said interactive region includeparticle beams, a charge converting magnet is oriented surrounding saidinteractive region to generate a magnetic field in said interactiveregion, and said particle beams excited in said interactive region areionized in said magnetic field.
 8. The optical interaction device asclaimed in claim 7, wherein said interactive region is oriented within aring of a ring accelerator and particles excited in said opticalinteractive region and ionized in said magnetic field are accelerated bysaid ring accelerator.
 9. The optical interaction device as claimed inclaim 1, wherein said interaction target introduced into said opticalinteractive region includes ion beams which generate multivalent ionsthrough interaction with said laser beams.
 10. The optical interactiondevice as claimed in claim 1, wherein said interaction target introducedinto said optical interactive region includes electron beams whichgenerate X-ray beams through interaction with said laser beams.
 11. Theoptical interaction device as claimed in claim 1, wherein saidinteraction target introduced into said optical interactive regionincludes gas which causes photolysis through interaction with said laserbeams.
 12. The optical interaction device as claimed in claim 1, whereinsaid interactive region is formed within a vacuum chamber and a duct forintroducing compressed gas into said vacuum chamber has a mouth directedtoward said interactive region.
 13. The optical interaction device asclaimed in claim 1, wherein said interaction target introduced into saidinteractive region is gas, said interactive region is formed within avacuum chamber, a duct is disposed within said vacuum chamber with itsmouth directed towards said interactive region, compressed gas isintroduced into said interactive region via said duct, an ion collectorguide is disposed in said vacuum chamber so as to collect ionizedmolecules of said gas, and said ion collector guide is electricallyconnected to a travel time mass analyzer for analysis of said molecules.14. The optical interaction device as claimed in claim 1, wherein alaser beam reflected by each said concave mirror in said first mirrorset is a converged laser beam focussing on said prescribed position onsaid common axis, and an optical interactive region of high photondensity is formed at said prescribed position by centralization offocuses of reflected laser beams.
 15. The optical interaction device asclaimed in claim 1, wherein a laser beam reflected by each said concavemirror in said first mirror set is a parallel laser beam focussing onsaid prescribed position on said common axis, and an optical interactiveregion of high photon density is formed at said prescribed position bycentralization of reflected parallel laser beams.
 16. The device asclaimed in claim 1, wherein a laser beam reflected by each said concavemirror in said second mirror set is a converged laser beam focussing onsaid prescribed position on said common axis, and an optical interactiveregion of high photon density is formed at said prescribed position bycentralization of focuses of reflected laser beams.
 17. The opticalinteraction device as claimed in claim 1, wherein a laser beam reflectedby each said concave mirror in said second mirror set is a parallellaser beam passing through said prescribed position on said common axis,and an optical interactive region of high photon density is formed atsaid prescribed position by centralization of reflected parallel laserbeams.